Just three weeks after officially splitting from her "Bachelorette" fiance of five months, Jef Holm, the reality star was spotted getting cozy with a new man: Nascar truck racer Jason White, 33, observers tell Us Weekly exclusively.

"They were all over each other," says a witness who saw the single mom, 26, and the Richmond, Va.-bred driver on a group date at the Nov. 3 Carrie Underwood concert in Charlotte, N.C. "Jason guided her through the crowd and held her hand as they walked downstairs." (They later ventured off alone to the club Suite, a source tells Us).